效绵鼎 Example:PDA-(2) The stack symbols: o Zo=start symbol.Also marks the bottom of the stack,so we know when we have counted the same number of 1’sas0's. 0 X=marker,used to count the number of 0's seen on the input. .11Example: PDA – (2) ◼ The stack symbols:  Z0 = start symbol. Also marks the bottom of the stack, so we know when we have counted the same number of 1’s as 0’s.  X = marker, used to count the number of 0’s seen on the input. 11